DESCRIPTION: A young investigator with a strong background in the study of myopia makes a revised application for experiments in the chicken and in an exciting new primate model - the marmoset - of the development of myopia and the regulation of ocular growth. The experimental design examines specifically the temporal pattern of eye growth in response to visual deprivation in the marmoset, whether the sign of retina defocus guides eye growth in the marmoset, and the role of accommodative control in the regulation of eye growth in both chickens and marmosets. The proposal seeks to establish whether there is a sensitive period for visual influences on eye growth, and to characterize the delay in ocular growth response following visual depravation started at different ages. Spectacles lenses will be used to induce defocusing in marmosets in order to study visual regulation of refractive state. Experiments will be conducted to determine whether changes in accommodative control result from induced changes in refractive state, or whether differences in accommodative control underlie differences in visual control of eye growth. These investigations will help provide data on the origin of the widespread problem of myopia in humans.